Datasheet LT8570, LT8570-1 (Analog Devices) - 6

LT8570/LT8570-1
PIN FUNCTIONS FBX (Pin 1):
Positive and Negative Feedback Pin. For a
RT (Pin 6):
Timing Resistor Pin. Adjusts the switching noninverting or inverting converter, tie a resistor from frequency. Place a resistor from this pin to ground to set the FBX pin to VOUT according to the following equations: the frequency to a fixed free running level. Do not float ( this pin. V ) R OUT − 1.204V FBX = ; Noninverting Converter 83.3µA
SS (Pin 7):
Soft-Start Pin. Place a soft-start capacitor here. ( Upon start-up, the SS pin will be charged by a (nominally) V ) 280k resistor to about 2.1V. R OUT + 3mV FBX = ; Inverting Converter 83.3µA
SYNC (Pin 8):
To synchronize the switching frequency to
VC (Pin 2):
Error Amplifier Output Pin. Tie external com- an outside clock, simply drive this pin with a clock. The pensation network to this pin. high voltage level of the clock needs to exceed 1.3V, and the low level should be less 0.4V. Drive this pin to less
VIN (Pin 3):
Input Supply Pin. Must be locally bypassed. than 0.4V to revert to the internal free-running clock. See
SW (Pin 4):
Switch Pin. This is the collector of the internal the Applications Information section for more information. NPN Power switch. Minimize the metal trace area connec-
GND (Exposed Pad Pin 9):
Ground. Exposed pad must ted to this pin to minimize EMI. be soldered directly to local ground plane.
SHDN (Pin 5):
Shutdown Pin. In conjunction with the UVLO (undervoltage lockout) circuit, this pin is used to enable/disable the chip and restart the soft-start sequence. Drive below 1.21V to disable the chip. Drive above 1.40V to activate the chip and restart the soft-start sequence. Do not float this pin. 85701fa 6 For more information www.linear.com/LT8570 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Package Description Revision History Typical Application Related Parts